There is accumulating evidence that oxidative stress may play a role in the pathogenesis of atherosclerosis. Unfortunately, there is relatively little information concerning the proximal, critical molecular pathways that are responsible for the altered vascular redox state in this disease. We have recently shown that vascular smooth muscle cells contain a hormone-sensitive NADPH/NADH oxidase that contributes to the control of the cellular redox state and mediates cellular hypertrophy, proliferation and inflammatory processes. During the current project period, in collaboration with Dr. David Lambeth, we cloned and characterized a new mitogenic oxidase, termed nox-1, that has high homology to the gp91phox subunit of the neutrophil NADPH oxidase. This oxidase appears to mediate platelet-derived growth factor (PDGF)- stimulated mitogenesis of vascular smooth muscle, but its role in other proatherosclerotic processes is unknown. In this project, we propose to characterize the role of nox-1 in processes that contribute to the pathogenesis of atherosclerosis. In specific aim 1, we will test the hypothesis that nox-1 mediates the response of VSMCs to growth factors, including migration, proliferation, and induction of inflammatory genes. Specific Aim 2 is designed to define on a molecular level the growth related molecular targets of nox-1 derived reactive oxygen species in VSMCs. In the third specific aim, we plan to determine whether nox-1 is expressed in atherosclerotic tissue, and define the cell types expressing nox-1 and producing superoxide. Finally, in Specific Aim 4, we will develop a transgenic mouse that overexpresses nox-1 specifically in vascular smooth muscle cells to assess the role of nox-1 in the development of atherosclerosis. Understanding the role of this new potent oxidase in vascular disease may suggest new therapeutic interventions targeted to nox-1.